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8Sci CH18
8th Science CH18 Fission and Fusion
Term | Definition |
---|---|
artificial transmutation | transmutation that does not happen spontaneously; scientists have forced nuclei to transmute by using particle accelerators, with the result that gaps in the periodic table have been filled and more than a dozen nw radioactive elements have been created |
chain reaction | reaction that can start if the neutrons freed by the split of one heavy nucleus into two lighter nuclei cause fission in other nuclei;in nuclear reactors, neutron-absorbing materials can be used so that fission chain reactions do not go out of control |
fission | nuclear reaction in which a large nucleus is split and energy is released; nuclear reactors produce electrical energy from a controlled fission chain reaction |
fusion | joining of smaller nuclei into larger ones; fusion of hydrogen into helium releases vast amounts of energy and is the energy powering the stars, including the sun; nuclear fusion is common in nature but not on Earth |
transmutation | occurs when an atom of one element changes to an atom of another element by spontaneously emitting a particle, or by decaying--which changes its number of protons and its atomic number |